Tutorial Ventilation 101

[Fitzera]

You have too much negative pressure in your tent if your temps are getting high and the walls are sucking in too much. You could try to hold the walls out, I believe some companies make supports for that. But if you can get more air entering your tent you will drop the negative pressure, lower your temps and keep the tent from trying to collapse.

I dont know which tent you use but I have a gorilla that has 3 inlet vents, when all 3 are closed it sucks in alot. One open is better. 2 open is more than enough.

 

[Insomniac420]

Thanks I have a bud box (badbox Imo)
150cm x 100cm x 200cm

 

[superpedro]

Its winter here and the air is super dry and cold. My seedlings and plants are anywhere from 2-4 weeks old. I'm not running the exhaust fan to allow the heater and humidifier keep the tent in the right zone.

So my question is:

How long would it take for the plants to use up the co2 before they need an air exchange? Based on roughly 151 cubic feet of space.
Normally I run the exhaust fan all the time, veg through flower, but this time I'm trying to be closer to the optimum vpd.

More curiosity than anything, I do open the tent one or two times a day to tend to things, so there is air exchange happening.

I wanted to show you something, but my plants are quite small, and I havent changed my 250MH to 600HPS yet.
But anyway, this does show a bit about CO2 uptake.
My tent is 120cm x 120cm x 200. Guess that is what you call a 4x4 in the US.
I have taken two pictures, ten minutes apart with the exhaust off, to show the difference.


First measurement.


Ten minuttes later.


When I try the same thing at full power, and a tent full of flowering girls, they eat up 100ppm in less than a minute.
You should NEVER go below 250ppm, since low CO2 slows down growth until it stops. This again can cause heatstress at even lower temps.

I found using ultrasound evaporation inline through the passive intake hoses, makes for much better efficiency. (you need to make sure water can drip from the hose though, as small droplets will collect inside the intake hose)


Here is something to think about in regard to fresh air.
Your cannabis dry matter is mostly carbon. Air contains less than 1/3 of a gram of pure carbon pr. cubic meter (aprox 35 cubic feet), and less than half of it i available for your plants. (Because uptake stops if it gets to low)

 

[Fitzera]

I wanted to show you something, but my plants are quite small, and I havent changed my 250MH to 600HPS yet.
But anyway, this does show a bit about CO2 uptake.
My tent is 120cm x 120cm x 200. Guess that is what you call a 4x4 in the US.
I have taken two pictures, ten minutes apart with the exhaust off, to show the difference.
[URL=https://www.icmag.com/ic/picture.php?albumid=82126&pictureid=2002756&thumb=1]View Image[/url]

First measurement.
[URL=https://www.icmag.com/ic/picture.php?albumid=82126&pictureid=2002754&thumb=1]View Image[/url]

Ten minuttes later.
[URL=https://www.icmag.com/ic/picture.php?albumid=82126&pictureid=2002755&thumb=1]View Image[/url]

When I try the same thing at full power, and a tent full of flowering girls, they eat up 100ppm in less than a minute.
You should NEVER go below 250ppm, since low CO2 slows down growth until it stops. This again can cause heatstress at even lower temps.

I found using ultrasound evaporation inline through the passive intake hoses, makes for much better efficiency. (you need to make sure water can drip from the hose though, as small droplets will collect inside the intake hose)
[URL=https://www.icmag.com/ic/picture.php?albumid=82126&pictureid=2002752&thumb=1]View Image[/url]

Here is something to think about in regard to fresh air.
Your cannabis dry matter is mostly carbon. Air contains less than 1/3 of a gram of pure carbon pr. cubic meter (aprox 35 cubic feet), and less than half of it i available for your plants. (Because uptake stops if it gets to low)

Thats cool, exactly what I was thinking about. I know I have enough co2 for this stage of growth without running the exhaust fan for air exchange, it just got me thinking and then my thinking produced that question which I couldnt answer for myself.

Very good info, thank you.

 

[Fitzera]

Thanks I have a bud box (badbox Imo)
150cm x 100cm x 200cm

I looked up those tents, it looks to me that each size design has inlet vents on opposite ends. I cant see how you are pumping out more air than those inlets let in, they look much larger than what is on my gorilla tent.

 

[Insomniac420]

Yes there is two intake passive vents
I have one open and tent sucks in
A lot there is no poles in middle of the tent
These would have helped

 

[Insomniac420]

This is the tent I have

 

[Fitzera]

Yes there is two intake passive vents
I have one open and tent sucks in
A lot there is no poles in middle of the tent
These would have helped

If the 2 vents arent allowing in enough air you could either;

a) turn down your fan if it has 2 run speeds via wiring, or dial.

b) throw a duct line in through the bottom sinch opening to allow more air in to closer match the rate of air pumping out.

That's all I've got for ideas, hope you get it dialed in.

 

[Insomniac420]

Thanks Fitzera I will try something out tomorrow

 

[Insomniac420]

Hey Icmag I am going to use a closet while
Workmen are here.

The closet is 86cm x 86cm x 200cm I have dimible ballast from 250 Watts to 660watts hps

I have 6ins extraction & wanted to no how big
Should my intake holes be.

Or should I buy an intake filter & fan

Thanks in advance

P. S I will be using an air cooled blazer reflector

 

[Snook]

Hey Icmag I am going to use a closet while
Workmen are here.

The closet is 86cm x 86cm x 200cm I have dimible ballast from 250 Watts to 660watts hps

I have 6ins extraction & wanted to no how big
Should my intake holes be.

Or should I buy an intake filter & fan

Thanks in advance

P. S I will be using an air cooled blazer reflector

intake at least 2 times the size of the intake.Passive intake, no fan. Xtra fan adds noise and heat. I just had a crew working for 4 days at my home. Lucky for me the owner of the business used to grow it and knew immediately what I was doing and reassured me of his silence. Did the workers realize what was going on? I think unless someone knows first hand what raw bud smell like they will not make the association. You dont mention a filter, that would be good addition to stealthe but again more noise and heat but worth it.

 

[Insomniac420]

Yes Snook I have a filter for extraction. I was going to try 3 x 6ins holes for passive intake
The extraction is 6ins

 

[wutwut]

what can go wrong if i use 8" fan at 40-60% of power with 6" ducting and cooltube in it? is there any heat problems then if airflow just rounds inside of ducting?

i'm planing to buy 8" sp mixed td-silent and add my old 6" ducting to it.

 

[Jock420]

Hey wutwut I have used 8in rvk. With 6ins phonic Trap ducting. I found less noise with
8ins phonic Trap ducting

 

[Dystans]

Hi everyone. Could anybody help me with vent wiring? I'm not sure, is N wire going to circuit board?

 

[grumpyavocado]

I made a post but maybe it's better to post here. Imagine this setup. A small 2ftx2ft tent with a 4" exhaust fan and a passive intake hole in a small room. Would it be ok to leave alone for 4 days with nobody in the house? Don't bother about other problems. I'm just asking about air.

 

[Snook]

I made a post but maybe it's better to post here. Imagine this setup. A small 2ftx2ft tent with a 4" exhaust fan and a passive intake hole in a small room. Would it be ok to leave alone for 4 days with nobody in the house? Don't bother about other problems. I'm just asking about air.

As long as you dont run out of air in that room you'll be good.

 

[grumpyavocado]

As long as you dont run out of air in that room you'll be good.

I forgot to add that the exhaust fan should blow air outside and the door in the room should be closed. Would enough air enter in the room?

 

[Snook]

I forgot to add that the exhaust fan should blow air outside and the door in the room should be closed. Would enough air enter in the room?

It's difficult to seal a room keeping air out for CO2 use. Air is some pretty slippery stuff, you'll be good. Are there plants in there?

 

[grumpyavocado]

It's difficult to seal a room keeping air out for CO2 use. Air is some pretty slippery stuff, you'll be good. Are there plants in there?

No, no plants in the house. Thank you for your help by the way!